The present invention relates to an apparatus for cutting lumber into desired length, comprising a log chain conveyor or the like for shifting a piece of lumber transversally, a transverse roller assembly for shifting the piece of lumber longitudinally, a plurality of stops which are steplessly shiftable in the longitudinal direction of the piece of lumber, and a circular saw or equivalent cutting device.
Cutting apparatuses are used in lumber trimming and grading plants. They are employed for eliminating a defective portion at the end of a piece of lumber under treatment. The defective portion must be cut off the lumber as accurately as possible, according to quality grading.
A lumber cutting device is known, in particular a butt end cutter, where the piece of lumber is transported in the longitudinal direction by means of rollers, to the desired cutting point. The correct transport length is generally measured by means of a separate measuring drum.
An apparatus is disclosed in the Finnish Patent Publication No. 58 735, which is particularly a butt end cutting apparatus, for cutting lumber steplessly into desired length. Bars are connected to the parallel conveyor chains of the apparatus, to which stops or counter-checks are installed at equal intervals. These are attached to the bar with bearings, and they can be turned in front of the piece of lumber in order to obstruct the longitudinal movement thereof. Moreover, in order to make it possible that the shifting of the piece of lumber in both longitudinal and transversal direction could take place steplessly for a desired length, the bar is constructed to be adjustable in its longitudinal direction by means of a movable guide or a groove, along which groove one end of the bar moves. The cutting of the piece of lumber is carried out according to the impulse received from the grader in such a manner that the basic cutting length is suitably defined by means of the counter-checks, whereas the additional length is determined by adjusting the guide and thus by moving the whole bar.
One drawback of previously known cutting apparatuses is their relatively great inaccuracy. This is the case particularly in the first-mentioned cutter. In the latter apparatus the measuring inaccuracy has been successfully reduced, but at the same time the apparatus has become more complicated. The functional security of neither apparatus is sufficient, especially when an operation is carried out at a high processing speed.